The invention relates to an apparatus for exchanging waste oil with fresh oil. More particularly it relates to the oil exchange apparatus for a device having an oil pan so as to circulate oil between the device and the pan, such as a hydromatic torque converter provided in motor vehicles.
The torque converter or automatic transmission comprises a pump impeller connected with an engine output shaft to drive, through actuating oil, a turbine impeller, which is connected with a sun-and-planetary gears transmission so as to change the output torque. Since such actuating oil is subjected to severe load, fatigued oil must be exchanged after the lapse of some time period.
Even if waste oil in pan of the torque converter is exchanged, there is still a some amount of waste oil remaining in the converter. It is, thus, necessary to drive the engine for a while, e.g. one minute for sucking up fresh oil newly supplied in the pan and exhausting waste oil remaining in the converter into the pan, whereby newly supplied oil is inevitably contaminated. Such treatment must be repeated at least a few or several times in order to almost completely exchange waste oil with fresh one.
Thus, an operator must thrust a hose nozzle for extracting waste oil to be taken into a can therefor and another hose nozzle for supplying fresh oil from another can alternately in the oil pan and each time actuate the respective pump and valve, which must be repeated a plurality of times. This is not only troublesome but also takes considerable time.
It has been found to our astonishment as a result of experiments that extracting waste oil and supplying fresh oil during idly driving the engine can attain an oil change in a fairly shorter time with far less labour.
Furthermore, in the past, flowmeters have been used for metering the amount of extracting waste oil and of supplying fresh oil. This is unsatisfactory in that there occurs a discrepancy between the both metered amount of extracted waste oil and supplied fresh oil, due to that the temperature of the waste oil in the oil pan is above 80.degree. C. while the temperature of the fresh oil is about 20.degree. C. and it comes to difference of the weight of metered oils, even if the volumetric amount of the oils are exactly metered by the flowmeters. It is another cause of the discrepancy that the flowmeter will operate when the hose nozzle sucks air due to, for instance, inadequate thrust the same in the oil pan.